JeffJS Console

Buy to Support JeffJS Console is a real JavaScript REPL for every Apple device — iPhone, iPad, Mac, Apple Watch, and Vision Pro. Pure-Swift engine, full ES2023, browser-shaped runtime, even on your wrist. WHAT IT IS A scratchpad for JavaScript that runs anywhere Swift runs, powered by a 1:1 port of QuickJS — about 70,000 lines of Swift you could step through in Xcode. No JavaScriptCore. No FFI. No opaque blobs. Type code, run it, see results. LANGUAGE COVERAGE Full ES2023: • Classes, modules, generators, async/await • Destructuring, spread, template literals • Optional chaining, nullish coalescing • BigInt, Symbol, Proxy, WeakRef • TypedArrays, ArrayBuffer, DataView • RegExp with named capture groups, lookbehind, Unicode mode • Dynamic import() BROWSER SURFACE Boots a window/document/fetch world without wiring anything up: • window, document, console, performance, crypto • fetch, WebSocket, IndexedDB • localStorage, sessionStorage • setTimeout, setInterval, queueMicrotask • TextEncoder, TextDecoder, URL, structuredClone, atob, btoa • A real DOM — HTML parser, CSS selectors, events, mutation callbacks THE REPL ITSELF • Persistent user globals — your variables survive between sessions • Command history with up/down navigation • Inline ghost-text autocomplete • Dot-completion that introspects live objects • A keyboard accessory bar for JS-friendly characters • Light, dark, and tinted icon variants ON YOUR WRIST JavaScriptCore isn't available on watchOS. JeffJS is. The bundled Watch App runs the same engine with the same language coverage as the phone. The complications widget shows your most recent eval result on your watch face. BUILT FOR PERFORMANCE On Apple Silicon, hot paths lift onto the GPU: • The garbage collector dispatches three Metal compute kernels above ~5,000 live objects (trial-decref → scan-rescue → collect-dead) • The regex engine compiles patterns into a flat NFA and tests every starting position in parallel via Metal • CPU fallbacks mean nothing breaks where the GPU isn't available OPEN SOURCE JeffJS is MIT-licensed and developed in the open. The full source for the engine, the console UI, the watch app, the test suite, and the tooling lives at github.com/jeffbachand/JeffJS — not just the binary you're downloading. Issues, PRs, and discussion welcome. WHO IT'S FOR • Developers who want a real JS scratchpad in their pocket • Anyone learning JavaScript who wants to try things without firing up a browser • Engineers who've ever wanted to run a script on their watch • Curious people who want to read how a JavaScript engine actually works my name is jeff.